Delete from End of Doubly Linked List in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a doubly linked list?

A doubly linked list is a chain of nodes where each node has two links: one to the next node and one to the previous node. This allows moving forward and backward through the list.

beginner

What happens when you delete the last node from a doubly linked list?

The last node is removed, the previous node's next pointer is set to NULL, and the list's tail pointer is updated to the previous node.

intermediate

Why do we need to update the previous node's next pointer when deleting from the end?

Because the last node is removed, the previous node becomes the new last node, so its next pointer must point to NULL to mark the end of the list.

beginner

What should you check before deleting from the end of a doubly linked list?

Check if the list is empty (head is NULL). If empty, no deletion is possible. Also, if there is only one node, deleting it makes the list empty.

intermediate

Show the steps to delete the last node in a doubly linked list.

1. Check if list is empty; if yes, do nothing.<br>2. If only one node, free it and set head to NULL.<br>3. Otherwise, move to the last node.<br>4. Update previous node's next pointer to NULL.<br>5. Free the last node.<br>6. Update tail pointer if used.

What pointer do you update when deleting the last node in a doubly linked list?

A The head pointer

B The next node's previous pointer

C The previous node's next pointer

D The current node's next pointer

When deleting the last node, the previous node's next pointer must be set to NULL to mark the new end of the list.

What should you do if the doubly linked list has only one node and you delete from the end?

A Do nothing

B Set head to NULL after freeing the node

C Set head to the next node

D Set previous node's next to NULL

If only one node exists, deleting it empties the list, so head must be set to NULL.

If the list is empty, what happens when you try to delete from the end?

A Nothing happens, no deletion

B Program crashes

C Deletes the head node

D Deletes a random node

If the list is empty (head is NULL), there is nothing to delete.

Which pointer in the last node is always NULL in a doubly linked list?

A Next pointer

B Previous pointer

C Head pointer

D Tail pointer

The last node's next pointer is always NULL to indicate the end of the list.

What is the time complexity of deleting the last node in a doubly linked list if you have a tail pointer?

A O(n)

B O(n^2)

C O(log n)

D O(1)

With a tail pointer, you can access the last node directly and delete it in constant time.

Explain how to delete the last node from a doubly linked list step-by-step.

Think about what pointers need changing and what happens to the list structure.

What are the edge cases to consider when deleting from the end of a doubly linked list?

Consider how the list looks in each case and what pointers must be updated.